This invention belongs to the field of agricultural chemistry, and provides new herbicidal compounds to the art. The growth of weeds, which are often defined as plants growing where they are not wanted, has well-known deleterious effects on crops which are infested with such plants. Unwanted plants growing in cropland, as well as in fallow land, consume soil nutrients and water, and compete with crop plants for sunlight. Thus, weed plants constitute a drain on the soil and cause measurable losses in the yield of crops.
The compounds of this invention are new to organic chemistry. Some compounds which have a relationship to the present invention, however, are known in the herbicidal art. Earlier workers have found herbicides among the pyridazinones, for example, U.S. Pat. No. 3,644,355. Some pyrimidinone herbicides have also been disclosed in the agricultural chemical art, such as the 6-alkyl-2,5-dihalo-3-phenyl-4-pyrimidinones of U.S. Pat. No. 3,823,135.
Some diphenyl-5-pyrazolinones have been disclosed, for example, the 3-methyl-1,4-diphenyl compound of Beckh, Ber. 31, 3164 (1898) and the 2-methyl-1,3-diphenyl compound of Knorr et al., Ber. 20, 2549 (1887). A pharmaceutical pyrazolinone is 2,3-dimethyl-1-phenyl-3-pyrazolin-5-one, called antipyrine, which was formerly used as an analgesic. Merck Index, 93 (8th ed. 1968).